In dealing with suicidal behaviors, the clinicians and researchers are confronted with the question: What are suicidal behaviors? Workers in this field have been handicapped by the lack of a uniform, coherent nomenclature and system of classification for describing suicidal behaviors. Our research is designed to test, refine, and expand the Schema for Classification of Suicidal Behaviors. This Schema divides suicidal behaviors into three categories: Completed Suicides, Attempted Suicides, and Suicidal Ideation. Within each category, the method used, if any, is designated, and ratings are made both of the seriousness of the patient's suicidal intent and the degree of medical lethality, i.e. the danger to life. Since the schema relies heavily on the concepts of intent and lethality, we will develop instruments to assess these variables objectively. A Suicidal Intent Schedule and a Medical Lethality Scale, both constructed for this purpose, will be used in the research and their reliability and validity studied. Follow-up data will enable us to judge the value of these instruments as predictors of future suicidal behavior. The Depression Inventory and the Optimism-Pessimism Scale, measures respectively of depression and hopelessness, will also enable us to study the relationship of suicide to depression and hopelessness as predictors of future suicidal behavior. Concurrently with our research, other centers will be involved in the utilization of the Schema. Thus, we will receive feedback from various sources concerning its usefulness for clinical and research purposes. This research should not only provide a foundation for the study of suicidal behaviors but should further our understanding of these behaviors.